In a conventional two-cycle engine used for motocycles or autobicycles, a suction pipe is so provided as to communicate with a crankcase and is connected with a carburetor through a tube made of rubber, and an air cleaner is connected with the carburetor so as to form an air sucking device. In such air sucking device, because the rubber tube is used for the connection, fastening bands are required and the tube is troublesome to fit and fasten. Particularly, in a small engine, the space is so small that the tube is difficult and inconvenient to fit, and fastening work and assembly is difficult. Further, there are disadvantages in that the vibrations caused by the engine and driving are transmitted to the connecting parts made of rubber to accelerate their fatigue and deterioration.
In such engine, a dead space will be formed on the upper surface or rear side of the crankcase and, if such space could be effectively utilized, it would be advantageous to small motor cars, motorcycles, or the like. On the other hand, even if an air sucking device is provided in such dead space as on the upper surface of the crankcase, a carburetor, which is complicated in contour and not so favorable in appearance, will be exposed and will not be preferable in appearance. In an autobicycle or motocycle, the engine and air sucking device would be exposed and would not be preferable in design. Further, if the carburetor, suction pipe, and connecting parts are exposed, they would not provide good protection. The present invention solves the foregoing problems.